Phantom limb in virtual reality

U.S. wars since 2001 have resulted in more than 52,000 Americans wounded in action. Among them have been over 1,600 major limb amputations. Then there are thousands more people who have lost limbs to accidents or disease. About 70 percent of amputees experience phantom limb pain, which can be chronic and debilitating.

The pain often spikes, resulting in unpredictable surges of intense pain that can disrupt sleep and activities of daily living. The pain can also interfere with their ability to use and control prosthetic limbs. A new treatment involving the use of virtual reality may offer another way of relieving this pain.

The mechanisms responsible for phantom limb pain are not clear, but the brain has sensory maps for different body parts. The ghost pain may stem from lasting representations of the lost limb in the brain. Current treatments include drugs, hypnosis, acupuncture and mirror therapy. Mirror therapy uses mirrors to trick the brain into thinking the patient has both arms, which helps alleviate pain. Obviously, mirror therapy would not work for those missing both arms. Current treatments do not always work, leaving some with debilitating pain for decades.

Scientists from Sweden did a study with 14 patients who had lost an arm and whose pain had not responded to other treatments. Electrodes attached to the nerves in the stump sent signals to a computer to control a virtual arm.

Patients saw a live image of themselves with the virtual arm. The patients were trained to use their thoughts to move the virtual arm, and they used it to control a virtual car in a racing game. They also played another game where they were asked to copy the movements of an onscreen arm with their own virtual arm.

The training requires the patients to use areas of the brain required for arm movement that may be entwined with circuits responsible for pain perception, thereby disentangling movement from pain.

After 12 two-hour sessions with the virtual arm, the patients had follow-up interviews after one, three and six months. Before treatment, these patients reported constant pain. However, for six months after treatment, patients reported an average of 50 percent reduction in pain and 50 percent reduction in the impact of pain on their sleep or daily activities.

One patient reported a gradual decrease in his pain to the extent that he eventually experienced pain-free periods. Rather than his hand feeling painfully clenched, it felt relaxed and open.

This virtual reality treatment trained the patient to control his missing limb, even when not hooked up to the computer and webcam. Using the nerves that formerly controlled a limb and the use of muscles in the stump that are otherwise neglected both may contribute to the relief of phantom limb pain.

This was a small study with no control group and a short follow-up period. A much larger controlled study of longer duration is planned to prove the therapy works. How many treatments do you know that allow you to play computer games as therapy?

Medical Discovery News is hosted by professors Norbert Herzog at Quinnipiac University, and David Niesel of the University of Texas Medical Branch. Learn more at www.medicaldiscoverynews.com.